The science behind this is because the stress-hormone called cortisol is released between 8am and 9am. The "stress" helps us get up and seize the day but if you add the stimulation of coffee when cortisol is already active the effect is lessened.

The bad news doesn't end there, drinking coffee at this time also means we build up a tolerance to caffeine and it's effects on us diminish over time.

So when should we be sipping on the good stuff? The study suggests between 9.30am and 11.30am, and between 1.30pm and 5pm. This is when your cortisol levels drop and the coffee is most effective, though if you're a lightweight when it comes to the arabica beans do take it easy.